Arrangement op arches in bridge-trusses



C. M. PENNINGTON, OF ROME, GEORGIA.

ARRANGEMENT OF ARCHES IN BRIDGE-TRUSSES.

Specication of Letters Patent No. 7,890, dated January 7, 1851.

To all whom t may concern Be it known that I, CUNNINGHAM M. PENNINGTON,of Rome, in the county of Floyd and State of Georgia, have invented anew and useful Improvement in Bridges; and I do hereby declare thefollowing to be a full, clear, and exact description of t-he same,reference being had to the accompanying drawings, making part of thesame, in which- Figure l, represents a side elevation; Fig. 2, a topview with portions of the upper cross bracing removed to exhibit thelower braces, door beams &c.; Fig. 3, an end view-` and Fig. t, asection through the red line mwofFig 1.

The same letters in all the figures represent similar parts.

The nature of my invention consists in a certain combination andarrangement of upright and inverted arches by which all thrust againstthe abutments or piers is prevented and at the same time securing apermanent structure.

To enable others skilled in the art to make and construct my bridge, Ishall proceed to describe the same.

On abutnients and piers of ordinary construction, I place the bearingtimbers a,

upon which are arranged the lower cords or stringers b,which extend thewhole length of the bridge unbroken, and at such distance or distancesfrom each other as the width of the bridge may require. These cords aremade in one continuous piece and framed together in any well knownmanner.

The upper cords CZ are constructed in a similar' manner with the lowerones, and the several cords are secured to each other, by the side crossbraces c, bottom cross braces g, and to-p bracing f, where the crossbraces lap over each other and over the cords and arches, I cut gains ofa suitable size in each, and the whole is secured at each of suchlappings with an iron bolt. There are two tiers of side braces on eitherside of the bridge, one set on one side of the cords and arches, and theother directly opposite, so that each bolt passes through the variouspieces constituting the side of the bridge. The bottom cross braces g,rest upon the cords H and are so arranged that their ends shall restupon the cords in the spaces between the side cross bracing e.

l/Vhere these bottom cross braces lap over each other, and over thecord, gains are cut in each piece, so as to make them immovable ineither direction, and the whole secured by a bolt at each and everysuoli lapping, as before described inthe manner of constructing the sidecross braces e.

The upper cross bracing f, is constructed in precisely the same mannerwith the lower ones, and rests upon the upper cord d, directly above andover the lower bracing. The ends o-f the upper braces project over thecords sufficiently far, to admit of being used as a support for therafters, and forms the eaves of the roof. The ioor beams t, are placed,and rest upon, the ends of the lower cross bracing as seen in Fig. l.

The arches z', z', z', c', which are made of plank put togetherflatwise, and sprung into the required curve of the arch while in courseof construction, throughout theseveral spans ofthe entire bridge, andare so arranged, as that they shall be alternately the upright andinverted arch through the whole length of the bridge, that is, the archwhich was the upright in the first span, will be the inverted arch inthe second span, and so on through its entire length, and vice versa,the arch which was the inverted arch in the first span, becomes theupright arch in the second span and so on through the entire length ofthe bridge, and are so arranged that one set of arches change fromupright to inverted over the piers, while the other set lchange midwayof the span. Directly over these crossing points of one set of arches,the other set are at their remotest distance from each other, and attheir strongest bearing or sustaining points, thus having two invertedand two upright arches in every portion of the bridgeso arranged thatwhile one set are approaching each other to change their direction atthe crossing points, where theyI are the weakest, the other set is inposition with regard to them, at their remotest distance from each otherand at their strongest sustaining point, thus distributing the weightupon the bridge evenly, and entirely preventing any cramping up inadvance of, or sinking below any heavy weight which may come upon it.Where these arches lap each other, or pass through between the doubleset of side braces, gains are continuous are cut in each piece, and abolt as heretofore described passes through the several pieces.

At the points m, n, on the arches, and Where they pass each other inchanging from the upright to the inverted, and from the inverted to theupright arch, I arrange chuck-arches 0, Z9, Which may abut against theinverted arch as at 7c, or against the cord as at Z. When they abutagainst the arch a piece of timber is placed between the arch and cordto relieve the arch of the Weight.

Where the cords or stringers pass the piers, I arrange pieces of timber7, let in flush With the side braces by means of gains, and boltedthrough the entire side as heretofore described in other parts of thebridge, for the purpose of strengthening the cords at that point.

Having thus fully described my invention, what I claim therein as newand desire to secure by Letters Patent, is-

The method herein described of combining and arranging the severalarches of a bridge, so as to make each arch alternately the upright andinverted arch, as it passes from one span of the bridge to another, andvice-versa, when one set of said arches have their remotest distancefrom each other, and their greatest sustaining point, directlyr over andunder the points Where the other set of arches are changing from uprightto inverted arches or Vice versa.

C. M. lENNINGrTON.y

Witnesses:

S. C. DoNN, E. RIDGWAY.

